Tunnel kiln



5 Sheets-Sheet 1 l Jn/venta? Wai@ Nov. 14, 1939. J. J. DuRxEUx TUNNELKILN Filed July 2, 1955 Nov. 14, 1939. J. J. DURIEUX 2,180,041

TUNNEL KILN Filed July 2, 1955 5 Sheets- Sheet 2 Nov. 14,4 1939. J. J.puRlEUx TUNNEL KILN 5 Sheets-Sheet 3 Filed July 2, 1935 Nav. 14, 1.939.J' J' DUREUX 2,180,041

TUNNEL KILN Filed July 2, 1955 ,5 Sheets-Sheet 4 Nov. 14, 1939.

J. J. DURIEUX TUNNEL KILN Fi1ed July 2, 1955 V 5 Sheets-Sheet 5 Fig. 3

Patented Nov. 14, 1939 UNITED STATES PATENT OFFICE Application July 2,

1935, serial No. zaszs In France July 2, 1934 17 Claims. (Cl. 25-'142)The present invention relates to improvements in tunnel kilns of thetype in which air for the combustion is fed-to the burners of theburning zone by means of the draft of the kiln, after having served tocool the baked articles. These improvements are intended to obtain abetter efficiency of the kiln and also to facilitate the operation andthe regulation-of said kiln. l The following arrangement has beenemployed in kilns of the kind above referred to: The air entering thekiln on the side from which the baked articles are removed is heated vbyits contact with said articles and then, moving on inside the kiln,reaches successively the burners distributed along the walls of thekiln. In this arrangement, ,the distribution of air to. the burnerstakes place in a very irregular manner. 'I'he burners that are closer tothe air inlet are fed with too great an amount of air while the otherburners do not receive a sufilcient amount of air or, more exactly, arefed with air which has lost a higher and higher amount of oxygen. Theselast mentioned burners may thus give a reducing llame which isdetrimental to the good working'of the kiln.

As the amount of air that is necessary for cooling the baked articlestreated in the kiln is -always greater than the amount of. airlnecessary for the' combustion of the gas at the burners, it has alsobeen suggested to by-pas's a portion of the air 4thus preliminarilyheated and to feed this portion to the preheating zone of the kiln. Thisresult was obtained by causing said portion ofthe air to iiow through apassage provided ,at the upper part of the kiln. This arrangement hasthe drawback of requiring, in the portion of the kiln subjected to thegreatest variations of temperature, the construction of superposedvaults for providing the passage in question, although this portion ofthe structure is liable to injuryv from many causes.

The chief object of the present invention is to provide a tunnel kilnwhich obviates these drawbacks.

An essentialv feature ofthe present invention consists in disposing theburners in parallel, on either side of the kiln,` these burners beingconnected with a main air conduit disposed laterally at the lower partof the kiln, along the burning zone of said kiln, in such manner thatthe heated air from the cooling zone iiows through said conduit and eachburner receives from said conduit, through an adjustable feed intake,the necessary amount of air, the fuel gas being` also supplied from amain conduit through an adjustable feed intake.

Another feature of the present invention consists in heating the airthat is admitted to the cooling zone of the kiln not by direct contactwith 5 the baked articles but by radiation from and conduction throughthe wall of a muiile extending along said cooling zone and separated.from the wall of the kiln by one or several' channels through which theair admitted to the kiln moves along a zig-zag path.

Still another feature of the present invention consists in evacuatingthe excess of cooling air through a passage provided in the top of thekiln and extending along the cooling zone thereof.

Still another feature of the present invention consists, in the case inwhich the fuel is'a gaseous fuel, in constructing. each burner withseveral nozzles, disposed in staggered arrangement, and parallel to theaxis of the kiln, with a view to obtaining .complete combustion at thevery outlet of the burner, so that the heat of the ilames may radiateover the greatest possible length of thel ware to be treated.

lStill another feature of the present invention lies in a specialconstruction of burners provided with a plurality of nozzles as abovementioned, this construction being applicable to burners for a tunnelkiln of any kind whatever.

Still another feature of the present invention consists inprolonging'under the preheating zone as far as the drying zone of thekiln the main air conduits which, on either side of the kiln, convey tothe burners the air that has been heated in the muille, with a view tofeeding into this drying zone hot air that contributes to the drying andthe heating of the varticles to be baked.

Stili another feature of the invention consists' in providing in therefractory platforms of the cars that carry the ware, longitudinalchannels o which are chiefly intended to distribute expan sion withoutproducing outward thrusts and which also serve to facilitate vthecirculation of hot gases under the ware.

Other features of the present invention will be seen to result-from thefollowing detaileddescri tion of a specific embodiment thereof. v

'A preferred embodiment of the present inven`== tion will be hereinafterdescribed with reference t'o the accompanying drawings, given merely by50 way of example, and in which: Fig. 1 is a diagrammatic verticalsection of the tunnel kiln; Fig. 2 is a horizontal sectional view on theline Fig. 3 shows on an enlarged scale a part of a cross section of thecooling zone of the kiln, on the line II-II of Fig, 1;

Fig. 4 shows in vertical section on an enlarged scale the part I0 ofFig. 2;

Fig. 5 is a vertical sectional view on the line III-HI of Fig. 4;

Fig. 6 is a vertical sectional view of a part of the kiln in the burningzone thereof taken on the line IV-IV of Fig. 1;

Fig. 7 is a transverse vertical sectional view on the line V-V of Fig.1;

Fig. 8 is a horizontal diagrammatic view of av burner according to thenresent invention:

Fig. 9 is a vertical section on the line VI--VI of Fig. 8;

Figs. 10 and 1l are an axial sectional view and a plan view,respectively, of a modification of the nozzle of a burner.`

The kiln illustrated by the drawings is a timnel kiln, employing a gasas fuel and in which the flames are of the naked type.

This kiln may include, in the known manner, a drying zone A, apreheating zone B, a burning zone C, in which are disposed the burners,and a cooling zone D. The ware carried by cars circulates through thistunnel kiln, entering for instance at I and moving inside the tunnel inthe direction of arrow 2, the baked articles being discharged at theopposite end of the kiln, that is to say at 3.

The air serving for the-combustion of the fuel is admitted into the kilnat this end 3, and it circulates in a direction opposed to that of themotion of the ware, as it will he hereinafter explained. y

The 'tunnel kiln, in the cooling zone thereof, designated byD (Figs. l,2 and 3), is constituted by an outer masonry work 4 and by an innerinutile 5 extending over the whole of said zone. 'This muiile is made ofhoneycomb bricks and is separated from the outer masonry work by spaces6, 6 in the lateral walls of the tunnel, and a passage 1 at the top ofthe tunnel. These spaces and this passage open into the atmosphere atthe end 3 and their oriilces may be more or less stopped by closingdevices not shown in the drawings.

The external air that is admitted into these spaces and which movestoward the burning zone o! the kiln heats up by contact with the vwallsof the muiiie and takes off from said walls the heat imparted thereto bythe baked articles.

'Ihe walls of the muiiie'are connected to the outer masonry work bycross members 6a (Fig.

3), which act as baiiles and compel air to move alc-ng a zigzag path.

'I'he cross sectional area of passages 6, G', and 1 for air increasesgradually from the end 3 of the tunnel toward the other end of thecooling zone, in order to correspond to the gradual increase of volumeofthe air' that is being heated in these passages.

Coldair 'penetrates into the passage 1 provided in the top part of thetunnel and circulates therein under the effect of the suction ofvertical conduit 8, mounted substantially in the vertical plane of theother end of the cooling zone, said conduit being connected either to achimney opening into the atmosphere or to a system of pipes for theheating of drying chambers or other rooms.

Cold w penetrates into spaces 6. 6' and circuiatcs therein either underthe action of the main aspirator, located-at 5, at a suitable point ofthe preheating zone, or under the action of an air blast forcing airthrough the inlet orices.

The air passages 6, 6 are provided at their ends with downwardlydirected connection passages Ill, Iii', of gradually decreasing crosssection, playing the part of Venturi tubes and shown on an enlargedscale in horizontal section and in longitudinal cross section in Figs. 4and 5 respectively. These connection passages open respectively into airiiues Il, Il', disposed laterally on either side of the kiln, along theburning zone thereof, in the lower part of thev masonry works. under thesets of burners I2, I2.

The burners I2 of a set of burners (Fig. 6) are fed with hot air fromair flue II through vertical conduits I3. The adjustmenteof therate offlow through these conduits is obtained by means of horizontal metallicregisters Il, operated from the outside by means of levers I5. The fuelgas is fed from conduit I8 through metallic tubes I'I, each of which isprovided with a regulating valve I8 and eventually with'a sight hole I9.The feed of the other set of burners I2' on the other side of the kilnis effected in an identical manner from hot air flue Il and gas conduitI6'. The burners are thus fed individually, each from a Aconduit of hotair and a conduit of gas, both of which are adjustable, which makes itpossible to obtain a predetermined mixture of air and gas at the veryoutlet of the burners.

Flues I I and I I' extend under the burning zone and beyond the endthereof under the preheating zone B. They lead either to the smokeexhaust 9 or,` beyond this point, tothe drying zone A when the articlestobe baked are'to be dried before entering the preheating zone. In thelatter case, the hot air circulating through the ues is distributed inthe drying zone of the kiln through a Y Aseries of vertical ascendingpassages 20, 20' (Figs. 2 to 7) the cross sections of which areadjustable by means of horizontal gates 2|, said passages opening intothe kiln at different levels. Hot air, i

after having absorbed the moisture present in the articles to be baked,is finally drawn, in thedirection of arrow 2, toward the suction device9 through which it is evacuated together with the smoke.

I might also provide, in the portion of the air ilues 'extending underthe preheating zone, vertical conduits branching oif from ilues II, I I'and opening 'into the kiln so as to allow a portion of the hot aircirculating through the air ilues to escape into said zone of the kilnin which it mixes with the gases.

In the preheating zone, the the gases is preferably rendered sinuousimmediately after the outlet from the burning zone by Vmeans of baiiies,consisting of refractory partitions 22, 22', disposed in staggeredrelationship (Fig. 2). This arrangement causes the gases to travel alonga zigzagushaped path in the horizontal plane and to dow moresatisfactorily along the articles that are being preheated.

An essential condition of good working of a tunnel kiln is the completecombustion of the gas serving for the heating of the kiln as this `gasescapes from the burners. In order to compath of travel of A ply withthis condition, and also in order to distribute the fiamesin the form ofan elongated curtain, as unito as possible, in the direction of thelength of the mln, the burners are given the form of the device shown inFig. 6 and, on an enlarged scale, on Figs. 8 and 9, which device has thefurther advantage of having a good resistance to the action of me. I

The gas, issuing from tube I 1, before entering burner I2, passes into amasonry `conduit; ,23, widening at its end at 2l (Fig. 8). Then said gasenters a chamber 25 and when issuing therefrom it draws hot air fromconduit I3 along with it, the whole then passing into the nozzle ornozzles of the burner. Instead of burners having each a single nozzle, Iemploy, preferably, burners including each several nozzles disposed instaggered relationship parallel to the axis of the kiln. At the top ofvertical-conduit I3, there is provided a plate 26, made for instance ofa ceramic material (Fig. 9) and provided with a plurality of taperednozzles 2'I. These nozzles, which serve for the inow of air, projectfrom the upper face of the plate. Above this plate 26 there is providedanother plate 28, also made of a refractory material and which forms oneof the walls of thechamber 25 into which the fuel gas 'is fed. Thissecond plate is provided with tapered holes which t upon nozzles 21,respectively, so as to form an arrangement similar to an ejector. Thefuel gas entering chamber 25 on the outside of nozzles 2'I enters thefurnace through the orifices of plate 28, drawing along, together withit, air from said nozzles.

The mixture of the two fluids that is formed at the outlet of nozzles 21can berendered more intimate in the following manner: The outer wall ofthe nozzles or the inner wall, or both (as shown in Figs. 10 and 11) areprovided with helical ribs, shown respectively at 33 on the outer walland at 34 on the inner wall.

The fuel gas, which flows along ribs 33, is given a rotary motion whichis combined with its as.

The respective burners maybe separated from one another by partitions 40(Fig. 6 extending inwardly close to the lateral sides of the stack ofware supported by the kiln cars.

Preferably, according to the present invention, the inner edges of thesepartitions are more and more remote from the sides of the stack of ware,as shown at 4Ia, Mb, Mc, etc., in the direction of ow of the gases, soas to afford a passage of increasing section for said -gases betweensaid respective edges and the lateral sides of the stack of ware.

When it is desired to bakeV the articles in a reducing atmosphere, thesearticles must be subjected, as soon as they enter tlie preheating zone,to the action of smoke containing an excess of unburnt gas. This kind ofatmosphere can be obtained in a simple manner with the kiln according tothe present invention by suitably ad-v the baking proper must take placein an oxidizing atmosphere use is made of means for feeding gas into thepreheating zone of the kiln.,

T hese gas feeding means supply gas, without burning it, as shown t 29',this ,reducing gas mixing with the smoke and travelling together with ittoward-the outlet.

'I'he ware is generally transported inside the kiln on cars the platformofwhich is made of a refractory material. Advantageously, this platformis provided with longitudinal channels, as explained. It will be forinstance constituted as shown by Fig. 7 of juxtaposed refractoryelements 30, leaving between them channels 3|, thecross section of whichis4 so chosen as to permit of easily passing a poke bar therethrough.

While I have, in the above description, disclosed what I deem to bepractical andeflcient embodiments of the present invention, .it shouldbe well understood that I do not wish to be limited thereto as theremight be changes made in the arrangement, disposition and-form of thepartsr without departingfrom the principle of the present invention ascomprehended within the scope of the appended claims.

What I claim is:

1. A horizontal tunnel kiln which comprises, in

horizontal passage provided in its wall, said passage opening directlyinto the atmosphere at one end of the kiln and into said collective airfeed means at the other end.

burner, and a cooling zone having at least one 2. A tunnel kiln whichcomprises, in combination, a burning zone, at least one row of burnersdistributed along said zone, one conduit at the lower part of said zoneextending in the longitudinal direction thereof, for feeding air to saidburners, means for connecting each'of said burners individually withsaid conduit, and a cooling zone having an air passage' in its sidewalls, throughout the/length of said4 zone, and of the .height of thestack of ware moving the tunnel,

said passage opening into the atmosphere at-l one end of the kiln andinto said air feed conduit fat the other vend.

3. A tunnel kiln which comprises, in combination, a burning zone, tworows of burners distributed along said zone, one on either side thereof,an air feed conduit below each row of burners extending, in thelongitudinal vdirection thereof, means for connecting each of theburners of a row individually with the air feed conduit loing at one endof the kiln into the atmosphere f the other end of the passage enteringinto one of :said conduits, respectively, and a preheating zonecommunicating with said burning zone whereby the burnt gases can passfrom said burning zone into said preheating zone.

4. A tunnel kiln according'to claim 3 further including partitionsprovided in each of these passages and extending overa portion of theheight thereof, said partitions being located alternately at the upperpart and at the lower part of said passage so as to cause air owingthrough said passage to move along a sinuous path.

5. A tunnel kiln according to claim 3 in which the cross section of eachof these passages-increases from theend thereof at which it opens intothe atmosphere toward the end thereof at which it opens into thecorresponding air feed conduit of the burning zone.

6. A tunnel according to claim 3 including between each of said passagesandthe corresponding air feed conduit a flaring passage the crosssection of which gradually decreases in the direction of ow of air, thatis to'say from the first mentioned passage toward the air feed conduit.

7. A tunnel kiln according to claim 3 in which tition elements beingdisposed in staggered relationship so as to compel the gases to movealong a sinuous path in a horizontal plane.

9. A tunnel kiln according to claim 3 in which the top of the coolingzone of the kiln is double walled so as to form therein a passage forcooling air, said last mentioned passage opening into the atmosphere atone end of the kiln and being of the full length and width of saidcooling zone.

10. A tunnel kiln according to claim 3 further including a fuel feedconduit under each row of burners, and means for individually connectingeach of the burners of one row to the corresponding fuel feed conduit.

11. A tunnel kiln according to claim 3 further including means forindividually adjusting the connecting means between each of the burnersof a row and the air feed conduit located below said row.

12. A tunnel kiln according to claim 3 further including a fuel feedconduit under each row of burners, means for individually connectingeach of the burners of one row with the corresponding fuel feed conduit,and means for separately adjusting said connecting means, respectively.

13. A tunnel kiln according to claim 3 in which said air feed conduitsextend below the preheating zone, and vertical passages connecting theinside of said preheating zone of the kiln with said prolonged portionsof the air feed conduits.

14. A tunnel kiln according to claim 3 further including a drying zonelocated adjacent said preheating zone, in which said air feed conduitsextend below said drying zone, and vertical passages connecting theinside of said drying zone with said prolonged portions of the air feedconduits.

15. A tunnel kiln according to claim 3 further including means foradjustably feeding combustible gas into said preheating zone.

16. A tunnel kiln according to claim 3 further including transversevertical partition elements between two consecutive burners of a row,said partition elements extending inwardly toward the axis of the kilnto a distance which decreases when moving inside the kiln toward thepreheating zone thereof.

1'7. 1n a tunnel kiln, a muille-like chamber arranged to permit passageof a stack of ware, and divided into a pre-heating zone, a heating zone,and a. cooling zone, gas burners arranged along each side of the heatingzone, an air chamber arranged at each side and immediately above saidcooling zone, said air chambers being open to the atmosphere at theouter end of the cooling zone, the air chamber above the cooling zoneending in a passage open to the atmosphere, the air chamber at the sidesof said zone ending in a passage which lies below the burners.-

JULES JOSEPH DURIEUX.

